Cold-cure flexible polyurethane foams are also referred to as “cold-cure foams” or “high-resilience foams (HR foams)”.
Highly elastic cold-cure polyurethane foams are widely used for producing mattresses, upholstered furniture or automobile seats. Such polyurethane foams are produced by reacting isocyanates with polyols. In the production of cold-cure flexible polyurethane foams, foam stabilizers serve to stabilize the expanding foam. The stabilizers ensure that a regular cell structure is formed and no defects occur in the region below the skin (i.e., sub-surface voids).
To produce cold-cure flexible polyurethane foams, polyethers, crosslinkers, polyisocyanates and also customarily auxiliaries, such as catalysts, stabilizers, blowing agents and the like are typically employed. In all prior art processes, the system has a high intrinsic stability due to premature crosslinking of the polyurethane foam. For this reason, it is possible or necessary in many cases to dispense with the use of a polysiloxane-polyether copolymer as an additive that stabilizes the foam against settling, since these foam stabilizers, which are indispensable in the production of “hot-cure foams”, lead to an unacceptable shrinkage tendency in the case of “cold-cure foams”.
There are many processes for producing highly elastic flexible polyurethane foams that have been comprehensively described in the literature. DE-A-25 33 074, which is fully incorporated by reference, cites many literature references that describe the industrial production of flexible polyurethane foams.
Furthermore, the production of flexible polyurethane foams is described in Becker/Braun, Kunststoff-Handbuch, Volume 7 (editor: G. Oertel), Polyurethane, Carl Hanser Verlag, Munich; Vienna; 2nd edition 1983, which is fully incorporated by reference.
Stabilizers such as siloxanes are usually not used as pure substances, but as a component of an appropriate formulation in order to improve the meterability or the ability to be incorporated into the reaction matrix. To dissolve the siloxanes, various organic substances are used as “solvents” for such formulations. DE-A-2 356 443 describes many organic solvents for the production of formulations comprising aralkyl-modified siloxane oils.
However, organic solvents are associated with a series of disadvantages such as a problematical toxicological classification, an excessively high flammability of the formulation and/or an undesirable emission of organic solvent residues from the resulting foam. Furthermore, the organic solvents can have an adverse effect on the properties of the cold-cure flexible polyurethane foam, e.g., pore structure, elasticity and the like.
The use of water has an advantage over organic solvents because water is available in virtually unlimited quantities, is nontoxic and is not flammable. Furthermore, water can easily be purified and disposed of without technical complications. A further advantage is that the storage of water is not subject to any significant safety regulations. Overall, the use of water as a solvent enables the complication and therefore the costs, of producing the cold-cure flexible foam stabilizer formulations to be significantly reduced compared to nonaqueous systems.
In view of the above, there is a need for providing cold-cure flexible foam stabilizer formulations that include water as a solvent.